What’s the latest Chicago has gotten a 70-degree day?

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Dear Tom,
What is the latest in the year it has taken for Chicago to log its first 70-degree day?
— Bryson Cook, Island Lake
Dear Bryson,
Our chilly spring is making everyone wonder if it will ever warm up. Chicago climatologist Frank Wachowski informs us that we are overdue as the average date for the year’s first 70-degree day is March 25. Checking the record books, the city’s latest first 70 was on May 7, 1874. However, back then and all the way through June 1942, the city’s official thermometer was located near the lake where chilly onshore winds often kept the mercury from reaching 70, while milder inland locations did. Since the city’s official site moved inland, the latest onset of a 70-degree day has occurred twice on April 25, first in 1951 and again in 1984. In contrast, Wachowski noted that the city’s earliest 70 was on Feb. 11, 1999.

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